Rent control has the efect of locking people in and reducing mobility, favoring those already in the market at the expense of those looking to get in to the market.
The obvious solution is to build more.
as far as i can tell, the effect of rent control in germany is mostly that similar properties cost a similar rent which does not prevent people from moving, because they are not risking an increase just because of the move.
Just look at Berlin. Try moving there now and see what options are available to you.
"The court ruled on Thursday that the Berlin government had overstepped its powers in introducing the law, as federal law governing rents was already in place."
this does not support an argument against rent control in general, but only against outright freezing rents in place which is what this law tried to do.
the stories about landlords getting around the rent limit by charging extra for furniture are also not helping the argument because the law covered that too, so they were effectively breaking the law. the only argument that is valid is the fact that less units were available for rent, showing that this particular law didn't work. but again, this does not prove that rent-control on general is bad.
german rent-control generally means that rent may not be charged higher than about 20% of the average rent in an area. this means that rents are still somewhat flexible and they can rise, but not excessively so.
Like honestly, rent control is just beyond dumb. There are like 1000 ways that actually solve the problem - but unfortunately they require cities and bureaucrats to work instead of just passing a law. Supply and demand. If it takes LONGER to get a building permit that to actually build a housing complex… When cities are not planning ahead creating new space (argh, infrastructure, public transportation, this sounds like work…